JPH0680967B2 - Optically controlled phased array antenna - Google Patents

Description

The present invention relates to an optically controlled phased array antenna.

[Prior Art] Figure 5 shows LP Anderson.
And F. Boldissar, “Antenna Beam Forming Using Optical Processors”
forming Using Optical Processor) "IEEE AP-S International Symposium Digest, AP11-3, pp431-434, 1987
FIG. 6 is a block diagram of a conventional optically controlled phased array antenna shown in FIG. 1, and FIG. 6 is a block diagram of a conventional light radiator 1 used in FIG.

In FIGS. 5 and 6, the micro signal which is the transmission signal is input from the oscillator 2 to the modulator 18 in the light radiator 1. On the other hand, the beam light emitted from the laser diode 19 is adjusted to have a predetermined beam width by the beam adjuster 20, and then enters the beam adjuster 22 via the beam splitter 21. The split light split by the beam splitter 21 is a modulator
Incident on 18. The modulator 18 shifts the frequency of the incident branched light by the frequency of the input microwave signal,
The modulated beam light is output to the beam adjuster 24 via the mirror 23.

The beam conditioner 22 adjusts the incident beam light to a predetermined beam width and then outputs it as the first beam light 3 to the image mask 6 via the mirror 5, while the beam conditioner 24
Adjusts the incident light beam to have a predetermined beam width d, and then outputs it as the second light beam 4 to the beam combiner 10. Here, as shown in FIG. 7, the relative amplitude of the second light beam 4 with respect to the position in the beam width direction is constant regardless of the position in the beam width direction.

The image mask 6 receives the incident first beam light 3
It is converted into beam light 7 having a beam shape corresponding to a desired antenna radiation pattern, such as a fan-shaped beam pattern, and emitted to the Fourier transform lens 8. For example, as shown in the figure, the Fourier transform lens 8 formed of a convex lens receives the incident beam light 7, and spatially Fourier transforms the amplitude distribution and the phase distribution (hereinafter referred to as the amplitude / phase distribution) of the beam light 7. After conversion, the beam light 9 having the beam width d is emitted to the beam combiner 10. The Fourier transform lens is described in, for example, Takahiro Ohgoshi, "Optical Electronics," edited by The Institute of Electronics, Information and Communication Engineers, The Institute of Electronics, Information and Communication Engineers, University Series, F-10, pages 55-58, published August 15, 1982. It is disclosed. The beam combiner 10 is the second
After combining the beam light 4 and the beam light 9 of
To the fiber array 12. Fiber array 12
The mixed light 11 incident on the fiber array 12 is spatially sampled, which is composed of a plurality of n optical fibers arranged in parallel in a plane so that the longitudinal directions of the optical fibers are parallel to each other at a predetermined interval. It is incident on each optical fiber.
The respective light beams incident on the respective optical fibers are respectively passed through the n optical fiber cables 13a to 13n to the respective photoelectric converters.
It is incident on 14a to 14n. Each of the photoelectric converters 14a to 14n makes the incident light beam the same as the frequency of the difference between the first light beam 3 and the second light beam 4, that is, the frequency of the microwave signal output from the oscillator 2. After the photoelectric conversion to a microwave signal having a frequency of, which is proportional to the amplitude of the input light beam and coincides with its phase, the amplifier
It outputs to the element antennas 17a to 17n arranged in a straight line or in a plane via 15a to 15n. Thereby, the microwave signal is radiated from the element antennas 17a to 17n to the space in the radiation pattern set by the image mask 6.

As described above, the beam light 7 emitted from the image mask 6 is Fourier-transformed once by the Fourier transform lens 8 into a Fourier transform image (that is, a Fraunhofer diffraction image) of the beam light 7, and then the element antenna 17a.
When radiated from an array antenna consisting of ~ 17n, the radiation pattern of the array antenna becomes a Fourier transform image (that is, Fraunhofer diffraction image) of the amplitude / phase distribution of the aperture. That is, since the amplitude / phase distribution of the beam light 7 radiated from the image mask 6 is Fourier-transformed twice, as is known, the amplitude / phase distribution of the beam light 7 is the far-field microwave radiated by the array antenna. This will uniquely correspond to the amplitude / phase distribution of the signal.

[Problems to be Solved by the Invention] In the optically controlled phased array antenna configured as described above, the radiation pattern of the micro signal radiated from the element antennas 17a to 17n depends on the shape of the image mask 6 and the optical axis. Set by position. Therefore, when the shape and position of the image mask 6 are fixed, the radiation pattern of the micro signal is fixed, and the radiation pattern cannot be changed.

By the way, since the diameter of a normal optical fiber is about 100 times the wavelength of light, it is not possible to make the arrangement interval of the optical fibers used in the fiber array 12 equal to or less than the wavelength of light, and the mixed light When 11 is sampled by the fiber array 12, the sampling interval becomes larger than the wavelength of light, which does not satisfy the sampling theorem. Therefore, the radiation pattern corresponding to the distribution of the Fourier-transformed beam light 9 cannot be accurately reproduced in the element antennas 17a to 17n, and therefore, the microwave signals radiated into the space from the respective element antennas 17a to 17n cannot be reproduced. The maximum sidelobe level in the radiation pattern is about −20 dB as shown in FIG. 8, and there is a possibility that interference or interference with a microwave signal of another communication system may occur. In order to prevent interference and interference, it is generally necessary to set the sidelobe level to -30 dB or less, for example.

In the above-mentioned conventional optically controlled phased array antenna, in order to realize a low sidelobe characteristic, the gain of the amplifiers 15a to 15n is controlled to control the element antenna 17a.
It is necessary to reduce the amplitude of the microwave signal fed to the element antenna in the peripheral part of the array antenna out of 17 to 17n. In order to realize this, it is necessary to use a plurality of amplifiers having different gains or individually adjust the gains of the amplifiers by using the amplifiers. There was a problem that it took time and money.

A first object of the present invention is to solve the above problems and to provide an inexpensive optically controlled phased array antenna which has a simple configuration and which can easily change the radiation pattern of a radio signal radiated from the array antenna. To provide.

A second object of the invention is to have low sidelobe characteristics,
An object is to provide an inexpensive optically controlled phased array antenna with a simple configuration.

[Means for Solving the Problems] The optically controlled phased array antenna according to the present invention is a first light emitting means (18a, 20a, 22) for generating and emitting a first beam light having a predetermined frequency. And second light emitting means (18b, 20b, 24) for generating and emitting second beam light having a frequency deviated from the frequency of the first beam light by the frequency of the input radio signal. )
And converting the first beam light emitted from the first light emitting means (18a, 20a, 22) into a beam light having a beam shape corresponding to the pattern shape of a predetermined antenna radiation pattern, and emitting the beam light. No. 1 conversion unit (6) and the beam light emitted from the first conversion unit (6) are received, and the amplitude distribution and phase distribution of the received beam light are spatially Fourier-transformed to obtain the Fourier transform. Second conversion means (8) for emitting the converted beam light, beam light emitted from the second conversion means (8) and emission from the second emission means (18b, 20b, 24) Combining means (10) for combining and emitting the second light beam, and sampling means for spatially sampling the light beams emitted from the combining means (10), converting the light beams into a plurality of light beams, and emitting the plurality of light beams. (12) and from the sampling means (12) Photoelectric conversion means (14a-14n) for photoelectrically converting a plurality of emitted light beams into radio signals and outputting the radio signals, and a plurality of radio signals output from the photoelectric conversion means (14a-14n) are radiated into space. Multiple antennas (17a
-17n), and a second light emitting means (18b, 20b, 24) provided between the second light emitting means (18b, 20b, 24) and the combining means (10). 18b, 20
b, 24) is provided with a distribution changing means (31) for changing the amplitude distribution in the beam width direction of the second light beam emitted from the b, 24) and emitting it to the synthesizing means (10).

In the light control type phased array antenna, the distribution changing means (31) is preferably the second
Is characterized in that the amplitude distribution of the light beam is changed so that the amplitude of the peripheral portion of the light beam becomes smaller than the amplitude of the central portion of the light beam.

[Operation] In the optically controlled phased array antenna configured as described above, the first conversion means (6) emits the first light from the first light emission means (18a, 20a, 22). Beam light having a beam shape corresponding to the pattern shape of a predetermined antenna radiation pattern is radiated, and the second conversion means (8) radiates from the first conversion means (6). The received beam light is received, the amplitude distribution and the phase distribution of the received beam light are spatially Fourier transformed, and the beam light after the Fourier transformation is emitted. On the other hand, the distribution changing means (31) is provided between the second light emitting means (18b, 20b, 24) and the combining means (10),
The amplitude distribution in the beam width direction of the second light beam emitted from the second light emitting means (18b, 20b, 24) is changed and emitted to the combining means (10).

Then, the synthesizing means (10) and the light beam emitted from the second converting means (8) and the distribution changing means (3).
The beam light emitted from 1) is combined and emitted, and the sampling means (12) spatially samples the beam light emitted from the combining means (10) and converts it into a plurality of beam lights. The photoelectric conversion means (14a-14n) that radiate
Respectively photoelectrically converts a plurality of light beams emitted from the sampling means (12) into radio signals and outputs the radio signals to the plurality of antennas (17a-17n). As a result, the plurality of radio signals are respectively transmitted to the plurality of antennas (17a-17
emitted from n).

Here, the second beam light is the distribution changing means (31).
Since the amplitude distribution in the beam width direction is changed by the beam width direction, the amplitude distribution of the beam light emitted from the combining means (10) is changed, whereby the radio waves emitted from the plurality of antennas (17a-17n) are changed. The antenna radiation pattern of the signal changes.

Further, when the distribution changing means (31) changes the amplitude distribution of the second light beam so that the amplitude of the peripheral portion of the light beam becomes smaller than the amplitude of the central portion of the light beam, the synthesizing means In the amplitude distribution of the beam light emitted from (10), the amplitude of the peripheral part of the beam light is smaller than that of the central part of the beam. Therefore, the plurality of antennas (17a
-17n), the level of the radio signal radiated from the antenna located in the peripheral part of the array antenna, which corresponds to the peripheral part of the above beam light, decreases, so the side lobe level in the antenna radiation pattern should be significantly decreased. You can

Embodiments Embodiments according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an optically controlled phased array antenna which is an embodiment of the present invention.

This optically controlled phased array antenna has the configuration of the conventional optically controlled phased array antenna shown in FIG.
It is characterized in that a distribution adjuster 31 composed of an ND filter for adjusting the amplitude distribution in the beam width direction of the second light beam 4 emitted from the light radiator 1 is provided.

As shown in FIG. 3, this distribution adjuster 31 has a so-called taper that changes concentrically such that the transmittance becomes maximum in the central portion of the beam light and becomes lower from the central portion to the peripheral portion. It has a transmittance distribution called the distribution. Therefore, the distribution adjuster 31 changes the amplitude distribution of the second beam light 4 in the beam width direction into the tapered shape to change the reference light.
It is emitted to the beam combiner 10 as 32. Therefore, the amplitude distribution of the beam light 11 emitted from the beam combiner 10, and the amplitude distribution of the microwave signal fed to the element antennas 17a to 17n are also the same as that of the reference light 32, and the beam of the beam light Element antennas (for example, 17a, 17n) that correspond to the peripheral portion in the width direction and are placed in the peripheral portion of the array antenna
The level of the microwave signal fed to the power supply is lowered. Therefore, the side lobe level of the radiation pattern of the micro signal emitted from the element antennas 17a to 17n to the space can be lowered as compared with the conventional case. The optically controlled phased array antenna shown in FIG.
It operates similarly to the conventional optically controlled phased array antenna shown.

FIG. 4 is a radiation pattern of the antenna when the amplitude distribution of the reference light 32 is a Gaussian distribution having an edge level of −7 dB, and the side lobe level is −30 dB or less,
Compared to the conventional example of FIG. 8, it is lower than 10 dB.

In the above embodiments, the distribution adjuster 31 is a concentric ND filter whose transmittance changes, but the present invention is not limited to this, and a concentric mirror whose reflectance changes, a lens for converging beam light, and the like. May be used. Further, instead of the image mask 6, a pinhole or an optical switch composed of a plurality of transmissive liquid crystal elements juxtaposed in a plane may be used. Further, as the element antennas 17a to 17n,
It is possible to use an array antenna in which a plurality of antennas such as a dipole antenna, a metal patch antenna formed on a dielectric substrate, and a horn antenna are linearly or planarly arranged.

Furthermore, by changing the transmittance characteristic of the distribution adjuster 31, it is possible to change the radiation pattern of the microwave signal radiated from the element antennas 17a to 17n. Therefore, there is an advantage that the radiation pattern can be easily changed and set.

FIG. 2 is a block diagram showing a second embodiment 1a of the light radiator.

In FIG. 2, a microwave signal which is a transmission signal is input from the oscillator 2 to the signal comparator 35 of the light radiator 1a.

In the light emitter 1a, the beam light emitted from the laser diode 18a is adjusted to a predetermined beam width by the beam adjuster 20a, then enters the beam adjuster 22 via the beam splitter 21a, and is branched by the beam splitter 21a. The split light 36a is incident on the beam combiner 33. On the other hand, the beam light emitted from the laser diode 18b is adjusted to have a predetermined beam width by the beam adjuster 20b, and then the beam splitter 21b.
Incident on the beam conditioner 24 via the beam splitter 21
The branched light 36b branched at b enters the beam combiner 33.

The beam adjusters 22 and 24 respectively adjust the incident beam light to have a predetermined beam width and emit it as the first beam light 3 and the second beam light 4, as in the conventional example.

The beam combiner 33 combines the two incident light beams and emits the combined light beams to the photoelectric converter 34. The photoelectric converter 34 photoelectrically converts the incident combined light into a microwave signal having a frequency of the difference between the branched lights 36a and 36b, and outputs the microwave signal to the signal comparator 35. The signal comparator 35 compares the microwave signal input from the photoelectric converter 34 with the microwave signal input from the oscillator 2, and outputs an error voltage signal proportional to the frequency difference between the signals to the laser diode 18b. . The excitation current of the laser diode 18b changes in response to this voltage signal, which changes the oscillation frequency of the laser diode 18b.

In the feedback control system configured as described above, the oscillation frequency of the laser diode 18b is controlled so that the frequencies of the two microwave signals input to the signal comparator 35 match. Therefore, the frequency of the difference between the frequency of the first beam light 3 emitted from the beam conditioner 22 and the frequency of the second beam light 4 emitted from the beam conditioner 24 is the micro frequency output from the oscillator 2. It is controlled to match the frequency of the wave signal.

The light radiator 1a configured as described above can be used in place of the light radiator 1 shown in FIG. 6, and in this case, the optically controlled phased array antenna of FIG. Operate.

EFFECTS OF THE INVENTION As described in detail above, according to the present invention, the optically controlled phased array antenna is provided with the distribution changing means for changing the amplitude distribution of the beam light in the beam width direction. It is possible to easily change the antenna radiation pattern of the generated radio signal.

In addition, the distribution changing means changes the amplitude distribution of the second light beam so that the amplitude of the peripheral portion of the light beam becomes smaller than the amplitude of the central portion of the light beam, so that among the plurality of antennas. Since the level of the radio signal radiated from the antenna placed in the peripheral portion of the array antenna corresponding to the peripheral portion of the beam light is reduced, the side lobe level in the antenna radiation pattern can be significantly reduced. Therefore, there is an advantage that the optically controlled phased array antenna having low sidelobe characteristics can be configured with a simple configuration and at a low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optically controlled phased array antenna which is an embodiment of the present invention, FIG. 2 is a block diagram showing a second embodiment of the optical radiator shown in FIG. 1, and FIG. Is a diagram showing the amplitude distribution characteristic of the reference light emitted from the distribution adjuster of FIG. 1, FIG. 4 is a diagram showing the antenna radiation pattern of the optically controlled phased array antenna of FIG. 1, and FIG. FIG. 6 is a block diagram showing the configuration of an optically controlled phased array antenna, FIG. 6 is a block diagram showing the configuration of a conventional light radiator, and FIG. 7 is a diagram showing the second beam light emitted from the light radiator shown in FIG. FIG. 8 is a diagram showing an amplitude distribution, and FIG. 8 is a diagram showing an antenna radiation pattern of the optically controlled phased array antenna of FIG. 1 ... Optical radiator 2 ... Oscillator, 6 ... Image mask, 8 ... Fourier transform lens, 10 ... Beam combiner, 12 ... Fiber array, 14a to 14n ... Photoelectric converter, 17a to 17n ... … Element antenna, 31… Distribution adjuster.

Front Page Continuation (72) Inventor Hisao Iwasaki Seika-cho, Soraku-gun, Kyoto Prefecture 5 Osamu Osamu, Mihiratani No. 5 Arai Optical & Radio Communications Research Institute, Inc. (72) Koji Yasukawa Seika-cho, Soraku-gun, Kyoto Prefecture Daisen, Osamu, Osamu, Minato, Hiratani No.5, ATR Optical Co., Ltd.

Claims (2)

[Claims] 1. A first light emitting means (18a, 20a, 22) for generating and emitting a first light beam having a predetermined frequency, and a radio wave inputted from the frequency of the first light beam. Second light emitting means (18b, 20b, 24) for generating and emitting a second light beam having a frequency shifted by the frequency of the signal
And converting the first beam light emitted from the first light emitting means (18a, 20a, 22) into a beam light having a beam shape corresponding to the pattern shape of a predetermined antenna radiation pattern, and emitting the beam light. No. 1 conversion unit (6) and the beam light emitted from the first conversion unit (6) are received, and the amplitude distribution and phase distribution of the received beam light are spatially Fourier-transformed to obtain the Fourier transform. Second conversion means (8) for emitting the converted beam light, beam light emitted from the second conversion means (8) and emission from the second emission means (18b, 20b, 24) Combining means (10) for combining and emitting the second light beam, and sampling means for spatially sampling the light beams emitted from the combining means (10), converting the light beams into a plurality of light beams, and emitting the plurality of light beams. (12) and from the sampling means (12) Photoelectric conversion means (14a-14n) for photoelectrically converting a plurality of emitted light beams into radio signals and outputting the radio signals, and a plurality of radio signals output from the photoelectric conversion means (14a-14n) are radiated into space. Multiple antennas (17a
-17n), and a second light emitting means (18b, 20b, 24) provided between the second light emitting means (18b, 20b, 24) and the combining means (10). 18b, 20
b, 24) a light control type characterized by comprising a distribution changing means (31) for changing the amplitude distribution of the second beam light emitted in the beam width direction and radiating it to the synthesizing means (10). Phased array antenna. 2. The distribution changing means (31) changes the amplitude distribution of the second light beam so that the amplitude of the peripheral portion of the light beam is smaller than the amplitude of the central portion of the light beam. The optically controlled phased array antenna according to claim 1.